DVCPro HD and DVCPRO 50 are not going to play in a DVCPro25 deck.
If your deck is a more advanced one that can play the HD and 50 meg flavors of DVC Pro, then I think all you need to do is go into the menu settings and change it to the correct format. Though a higher end DVC pro deck should be auto-detecting the format and adjusting to play it. You can also set a menu pref for that, I think.